New Viral Emergence in Marine Mammals: Another Consequence of Arctic Warming
Jennifer Thomson
Tracey Goldstein is a truly impressive woman. Acting director of the One Health Institute at UC Davis, seasoned Arctic seal-tagger, and studier of marine mammal health and pathology; she is now the author of a Nature article, linking the reduction in Arctic sea ice to the emergence of Phocine distemper virus in marine mammal populations in the Pacific. Here, we interviewed her on her research activities, and her amazing journey all over the world to get to where she is now. Settle yourself in for a long read, and enjoy!
Hey Tracey! Tell us a bit about yourself
Ooh where to begin? I am a professor and associate director (currently acting) of the One health Institute here at UC Davis. I have worked with marine mammals for most of my career, and I have always been interested in health and disease. I have worked in California, lived up in Alaska, and studied seals and sea lions in Russia! My daily research consists of studying diseases, biotoxins, and health in marine mammals, terrestrial animals, and people.
Your studies have taken you from marine mammal biology to pathology! What led you to become interested in these topics, and did you find it difficult to merge these two areas of very different biological scales together?
Good question! I grew up in South Africa just outside Johannesburg, and being an animal-lover, always thought I wanted to be a vet. One summer at the beach, I found a penguin that was hurt, and I took it to a rescue and rehabilitation centre. That was the first time I thought about the health of marine mammals! Later, I moved to the US (I did my undergraduate degree at UC Santa Barbara), and really got interested in understanding animal health when I volunteered at a marine mammal rehabilitation centre. Here, I worked with many stranded seals and sea lions. By the time I did my PhD at UC Davis, I had already seen animals exposed to lots of different viruses, and also animals dying from many different diseases. Thus, I was curious about how marine mammals became infected, and the physiological consequences. I therefore took the opportunity to bring both of my interests in pathology and marine mammal health together. This does mean that I am not a specialist in any area (which can sometimes be hard - to know a little about a lot of things!), but I am lucky to work with a great team, who all support each other.
You often tag seals up north in the Arctic! What led you to become interested in the Arctic as a place of pathogen surveillance specifically? and I have to ask: how on earth do you go about sampling and tagging a seal?
After my PhD, I got a postdoctoral position at the Alaska SeaLife Centre, to understand the health of the local wildlife, collaborating with scientists at NOAA, the US Fish and Wildlife Services, and the US Geological Survey. At the time, there was a decline in the population of Northern sea otters, and we wanted to understand what was happening from a health and disease perspective. My work consisted of capturing sea otters, and testing them for a number of pathogens, to see what they had been exposed to. Unfortunately, this was first time we found Phocine distemper virus in sea otters; but which led us to try and understand how sea otters (and potentially other animals) were infected. From there, these investigations eventually led me to my recent research in the Arctic!
As for how we capture and tag seals: well, it depends! When I was working with harbour seals, we used hand (salmon) nets or seine nets with small boats to capture them in the water. On the ice, we would sneak up behind them and capture them with a salmon net. It also depends where we are, how big the seal is, how many people are on your team, and if the seal needs sedating. We try to minimize the time from capture to releasing the animal to under 20/30 minutes, to reduce stress for the animal. Swabs and blood samples will usually take around 10 minutes, but if you are tagging a seal, this can take a little longer. The image below is of myself waiting beside a seal after a tagging procedure – I’m waiting for the glue to dry and the animal to be awake enough to return to the water.
Dr. Tracey Goldstein as part of the team capturing, sampling, and tagging seals in the Bering Sea back in 2009. Photo: NOAA Fisheries, Polar Ecosystems Program, AFSC.
Have you found that the links between climate change and marine mammal health appear to less publicised than, coral reef acidification, for example?
You’re right! Few papers talk about sea ice reduction and how that may affect the health of marine mammals, but on land we know there are quite a few examples that link climate change and diseases. The ocean and the Arctic are hard places to study and collect data – there has been some speculation on climatic-instigated health consequences previously, but now we have collected data regarding viral movement. Alaskan communities have been very aware of the changes in the Arctic, and hunters have been noticing for years changes and decreases in sea ice trends, but they currently don’t always have a big enough voice to spread awareness. Personally, I think that: as climate change is changing things so quickly up there, these stories are going to be told more often. For example, last year there was almost no ice bridging Alaska and Russia, and in remote areas of Alaska; coastal communities have already been relocated due to increases in sea level. As technology improves, and we can get up into the Arctic and monitor things more efficiently, we will probably find a similar association between climate change and other marine pathogens, just as we find in terrestrial environments.
Tell me about your most recent paper (published in Nature!). What are the different ways in which the reduction of Arctic sea ice can cause a spread of Phocine distemper virus (PDV)?
In 2004 we found in PDV in sea otters. This was surprising, as these animals typically do not travel long distances and we actually sampled the animals quite far south off Kodiak Island. We did not understand how a virus that had previously only been seen in the Atlantic made it to the Pacific. We wondered if animals that didn’t usually meet were now able to come in contact with each other to exchange viruses. A way this could happen is via sea ice openings to facilitate movement. In 2002 there was also a large outbreak of PDV seen in harbour seals in the Atlantic, where an estimated 50% of the population died. This outbreak reached a peak in August and September: the time of year with the minimum Arctic sea ice extent! Previously, this virus had also caused an outbreak in the Atlantic in 1988, but there was no sign of the virus in the Pacific at that time. Therefore, we wanted to see what had changed between these two dates.
Looking at satellite data, there seemed to be drastic reductions in sea ice between 1988 and 2002, where open channels could facilitate movement between populations. Could this be how the virus came across? We tested archived samples, and also sampled animals for the virus in 2009, in order to see:
When the virus was introduced
What animals were affected. Could multiple species be infected, and could the channel (due to melting sea ice) be the way PDV was passed over?
Our antibody / PCR / movement tag data supports our suspicions! Sometime after 2002, PDV was first introduced. In 2009, both fur seals, and sea lions were also PDV positive. This was the evidence that showed multiple animals could be infected with the virus by coming into contact with each other. In both years studied, the peak infection was associated with years in which there was an opening in the ice. The more this occurs, the more opportunity there will probably be for viruses / other pathogens to move.
Potential routes for movement of seals infected with PDV through the Arctic Ocean opened by reductions in sea ice extent. Routes along northern Russia (green) and northern Canada (orange) are shown with August 2002 sea ice extent. Changes in historic sea ice barriers may facilitate Arctic and sub-Arctic seal movement and contact that was not possible in years prior to PDV detection, allowing for introduction of PDV into the Northern Pacific Ocean. Photo: Elizabeth VanWormer.
Are there any ways we can mitigate Arctic viral emergence via veterinary / conservation methods on the ground (apart from ‘normal’ climate change mitigation methods)?
As humans, we all need to reduce our climate footprint, but I think that is a different question! To protect animals from PDV, we can do two things. Firstly, when there was an outbreak (the most recent being in 2018 in the US), sick animals were vaccinated with a canine distemper vaccine, to protect them from PDV (after they were rehabilitated and before they were released). Secondly, you can protect small endangered populations, if you are worried that a virus could wipe out a vulnerable population. For example, NOAA has vaccinated wild Hawaiian monk seals in the event they get exposed to the virus. However, when you think about the large scale of the Arctic, it is not realistic to vaccinate all animals, as cost and accessibility are factors! We are thus very lucky to have a vaccine such as canine distemper that can be used as a cross-protection measure for marine mammals, as it is not really feasible for pharmaceutical companies to make a vaccine purely for seals!
Adult male ribbon seal on the ice. Photo: NOAA Fisheries, Polar Ecosystems Program, AFSC.
You now work as Associate Director at the One Health Institute Laboratory, UC Davis, which is amazing! Please give a brief overview of the institute’s aims.
Many of us that work here are involved in different projects that examine the health of the environment, animals, and people together; it is hard to separate these aspects. When working in public health, one recognises that the focus cannot just be on animal health alone, as all the other factors play a role too. So, our mission is to look at problems holistically, and bring in the right team of people to solve large problems. This is the main theme behind One Health: to answer big questions, we need diverse teams which include virologists, biologists, vets, economists, and social scientists - all working together.
Do you think that the concept of One Health will appear more in future conservation rhetoric?
I think so! As the world deals with bigger and more complex problems, it is hard to tackle one side only. For example, I’ve also been working for 10 years in Africa and Asia - places where animals, people and the environment are so closely connected! We are working hard with local governments to create ‘One Health’ teams of doctors, vets and biologists to solve problems collectively. Climate change, migration, war, deforestation: all these things are global issues that will affect both individual and planetary health; thus, we cannot study them separately. The One Health idea is here to stay.
Tell us about your most recent science and outreach exploits. How important do you think it is for young schoolchildren, and especially for girls, to be inspired by scientists?
It is super important, as this inspires change at the grassroots level. Recently, I was invited to a girls STEM summer camp in Lake Tahoe. I also work with bats (in the aforementioned project based in Africa and Asia!), so I brought nets; put the girls in protective gear / masks, and we ‘caught’ (plastic) bats and safely removed them from the nets! It was a great opportunity to expose them to fieldwork, and for them to get the chance to ask me questions about my role. It was such a great day. I find it so exciting to see young girls excited about science and STEM!
The ocean has changed rapidly in the last couple of decades. Could you leave us with any last words of wisdom concerning ocean conservation?
That’s a big question! For myself as a human, I try to figure out how to be a good citizen. I try to think about the ways in which I can reduce my carbon footprint to decrease global warming, in whatever small way I can. It can feel really overwhelming if you think that you have to stop it by yourself! So, focus on the little individual things each of us can change. As a scientist, it is important to study our own systems, but we also need talk to each other about other related research, so we can see the bigger picture. For example, it is all well and good studying marine mammals, but how are the seabirds faring?
You can follow Tracy on Twitter at @DrTracGoldstein or @OneHealthLab, ad on Instagram at @onehealthinstitute. To read the full article in Nature, click here. Check out the One Health Institute Laboratory website to find out more about their current research projects.
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